The present invention relates to an improved gas laser tube assembly for a C0.sub.2, CO, or other gas laser.
In the past the conventional way of making a gas laser tube has been to glass blow the tube including the various seals or fittings thereof. However, this type of glass blown tube is problematical because it is subject to breakage at the hose fittings, vacuum fittings, etc. during shipping and assembly, and also because of the difficulty in removing and cleaning electrodes used with the tube.
In an attempt to avoid the aforementioned problems associated with glass blown tubes, it has been proposed to employ non-blown glass tubes in the form of straight pieces of glass pipe with special fittings in the form of concentric metal sealing rings being provided on the ends of the glass pipes for sealing purposes. However, this known arrangement is disadvantageous in that disassembly thereof requires pulling the laser mirror mount off thereby requiring realignment of the laser mirror when reassembling. Further, such a disassembly operation requires breakage of the coolant oil seal and draining of the coolant oil which can be a messy, time consuming operation wherein it is possible to spill oil into the plasma tube bore.
An object of the present invention is to provide an improved gas laser tube assembly which avoids these problems associated with known laser tube assemblies. More particularly, an object of the invention is to provide a gas laser tube assembly which permits pulling out the laser tube without destroying the laser alignment or changing the alignment of the laser mirrors.
A further object of the invention is to provide a gas laser tube assembly wherein it is unnecessary to break the seal to the liquid coolant as in the prior art arrangements to clean, repair or replace electrodes.
Another object of the invention is to provide a gas laser tube assembly wherein the opposite ends of the plasma tube are subjected to essentially equal cooling and wherein the electrodes at the respective ends are of equal mass thereby allowing either end of the tube to function as a cathode so that the laser tube can be run on either alternating or direct current. While most gas lasers are operated with direct current, alternating current may be desirable in certain low cost applications or where 120 pulses per second are desired. In the past, gas laser tubes have generally not been balanced in mass and cooling at each end.
A still further object of the present invention is to provide a gas laser tube assembly which results in improved optical axis alignment between the plasma tube and the adjacent end structure of the assembly.
These and other objects of the invention are attained by providing a gas laser tube assembly comprising an elongated gas laser plasma tube, a member positioned adjacent one end of the elongated gas laser plasma tube in spaced relationship thereto along the longitudinal axis of the plasma tube, and releasable connection means extending between and releasably connecting the one end of the plasma tube and the member in spaced relationship along the longitudinal axis of the plasma tube, the connection means and the member being arranged for telescoping movement with respect to one another in either direction along the longitudinal axis of the plasma tube at least upon release of the connection means thereby facilitating removal and installation of the plasma tube from the assembly.
In a disclosed, preferred embodiment of the invention the member positioned adjacent the end of the elongated gas laser plasma tube includes a bore which serves as a gas port for conveying gas to or from the interior of the plasma tube by way of a cooperating passage provided in the releasable connection means. The bore in the member and the cooperating passage in the releasable connection means extend in a direction essentially coaxial with the longitudinal axis of the plasma tube.
The bore in the member extends completely through the member and the end of the member opposite the plasma tube includes means for connecting a mirror or an additional gas laser plasma tube to the member. With this arrangement, upon release of the releasable connection means, the plasma tube can be removed and reinstalled in the assembly without destroying the laser alignment or requiring realignment of the laser mirror when reassembling.
According to a further feature of the disclosed embodiment, the releasable connection means includes a first part connected to the one end of the plasma tube and a second part releasably connected to the member with means being provided for releasably connecting the first and second parts to one another. The first part includes an electrode attached therewith, the electrode having a bore extending therethrough in a direction essentially coaxial with the longitudinal axis of the plasma tube. The one end of the plasma tube is bell-shaped to accommodate at least a portion of the electrode therein.
The gas laser tube assembly of the disclosed embodiment further includes a cooling jacket surrounding the plasma tube in spaced relationship thereto so as to define a coolant passage between the cooling jacket and the plasma tube. Means are provided for connecting one end of the cooling jacket to the first part. More specifically, the outer surface of the one end of the cooling jacket is conically shaped and the means for connecting the one end of the cooling jacket to the first part includes a conical cooling jacket sealing ring surrounding the conically shaped one end of the cooling jacket and threadedly attached to the first part, a compression ring positioned between the sealing ring and the outer surface of the conically shaped one end of the cooling jacket and an O-ring seal positioned between the first part and an end surface of the one end of the cooling jacket. The first part includes a passage for conveying a fluid coolant to or from the coolant passage. By connecting the cooling jacket and the electrode to the first and second parts, respectively, of the releasable connection means, it is possible to remove the electrode from the assembly for cleaning, repair or replacement or to clean the interior of the plasma tube without distrubing the integrity of the coolant passage. Because of this and the fact that the plasma tube can be readily removed and reinstalled in the assembly without destroying the laser alignment, it is possible to remove the plasma tube from the assembly and service the electrode and the interior of the plasma tube in a very short time without risk of oil contamination in the plasma tube bore.
The connection between the first part and the one end of the plasma tube is a releasable connection made by means of a plasma tube sealing ring which is threadedly attached to the first part with an O-ring seal being positioned between the sealing ring and the first part and engaging the outer surface of the one end of the plasma tube.
It is another feature of the invention that an assembly of the type described is provided at each end of the elongated gas laser plasma tube thereby facilitating removal and reassembly of the plasma tube for servicing the electrodes or cleaning the interior of the plasma tube without disrupting the intergrity of the coolant passage between the plasma tube and the outer cooling jacket and without requiring realignment of the laser. Also, with the uniform cooling provided by this overall arrangement and with the use of electrodes at each end having equal mass, the laser can be run on either alternating or direct current since it is balanced in mass and cooling at each end.
A still further feature of the illustrated embodiment is that the second part of the releasable connection means includes a tubular projection at its end opposite the plasma tube. The tubular projection surrounds and is essentially coaxial with the bore in the second part and is telescopically positioned within the bore or gas port of the adjacent member. The releasable connection means includes means for releasably sealing the tubular projection in a gas-tight manner in the bore of the adjacent member. This means includes a tubular projection sealing ring threadedly attached to the adjacent member and an O-ring seal positioned between the adjacent member and the sealing ring and engaging the outer surface of the tubular projection. When sealing pressure upon the outer surface of the tubular projection is released, the connection means and the adjacent member can be telescopically moved with respect to one another in either direction along the longitudinal axis of the plasma tube to facilitate removal and installation of the plasma tube from the assembly.
Where this type of arrangement is provided at each end of the plasma tube, upon release of the connection means the plasma tube can be moved laterally along the longitudinal axis of the plasma tube toward one adjacent member at a first end and away from an additional adjacent member at its second end so that the tubular projection at the second end moves out of the cooperating bore of the additional member. Thereafter, the second end of the plasma tube can be swung out of alignment with the gas port of the additional member. The plasma tube is then moved in the opposite direction to completely remove the plasma tube from the member adjacent its first end. Reinstallation of the plasma tube is accomplished in a similar fashion by reversing this sequence. The invention thus permits disassembly and reassembly without destroying the alignment of the mirrors or adjacent plasma tubes connected with the member and additional member.
According to another feature of the invention the leading end of the tubular projection received in the gas port is inclined with respect to the longitudinal or optic axis of the plasma tube. This conditions the gas flow through the plasma tube and cuts down on internal stray radiation.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, one preferred embodiment in accordance with the invention.